Question 1

Which enzyme is responsible for converting ATP to cyclic adenosine monophosphate (cAMP) in the cAMP signaling pathway?

Accepted Answer

Adenylyl cyclase

Question 2

What is the primary function of cAMP in cellular signaling?

Accepted Answer

It acts as a secondary messenger to activate cAMP-dependent protein kinase A (PKA).

Question 3

How many cAMP molecules are required to fully activate one PKA holoenzyme?

Accepted Answer

Four cAMP molecules, two for each regulatory subunit.

Question 4

Which of the following best describes the sequence of events leading to PKA activation after adenylyl cyclase is activated?

Accepted Answer

cAMP binds to regulatory subunits, causing release of catalytic subunits that phosphorylate targets.

Question 5

What is the role of phosphodiesterase in the cAMP/PKA signaling pathway?

Accepted Answer

It degrades cAMP, terminating the signal.

Question 6

A mutation in the regulatory (R) subunit of PKA prevents cAMP binding. What is the most likely consequence?

Accepted Answer

PKA cannot be activated by cAMP.

Question 7

Which of the following steps is NOT involved in the activation of PKA?

Accepted Answer

ATP is converted to cAMP by PKA.

Question 8

If a cell has 1000 molecules of PKA holoenzyme and each requires 4 cAMP molecules for activation, how many cAMP molecules are needed to fully activate all PKA holoenzymes?

Accepted Answer

$$1000 	imes 4 = 4000$$

Question 9

Which statement about the structure of PKA is correct?

Accepted Answer

PKA is a tetramer consisting of two regulatory and two catalytic subunits.

Question 10

What is the function of a phosphatase in the context of protein phosphorylation?

Accepted Answer

A phosphatase removes phosphate groups from proteins.

Question 11

Which of the following would most likely result from a mutation that keeps the PKA regulatory subunits in the active state?

Accepted Answer

PKA catalytic subunits would remain inactive.

Question 12

Which of the following is a direct cellular response to PKA activation?

Accepted Answer

Phosphorylation of target proteins leading to changes in cell function.

Question 13

Which step in the cAMP/PKA pathway is regulated by feedback inhibition?

Accepted Answer

Degradation of cAMP by phosphodiesterase.

Question 14

What is the effect of cAMP binding to the regulatory subunits of PKA?

Accepted Answer

It causes the release of the catalytic subunits, activating PKA.

Question 15

Which of the following is a common misconception about the cAMP/PKA pathway?

Accepted Answer

cAMP directly phosphorylates target proteins.

cAMP and Protein Kinase A (PKA): Mechanism, Activation, and Regulation

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